" Although gravitation is an important force in the immediate environment of large objects like trees and human beings, it is not felt by bacteria in a liquid medium. For them, because of their size, Brownian motion is a dominant environmental factor, while we are not buffeted to and fro by bombarding molecules. But that size disparity is a consequence of genetic differences between life-forms, so just as environment is a factor in the development of an organism, so genes are a factor in the construction of the environment. "

― Richard C. Lewontin , Biology Under the Influence: Dialectical Essays on Ecology, Agriculture, and Health